The present invention generally relates to a rapid thermal heating apparatus for heating substrates and, more particularly, to a heating apparatus for heating semiconductor substrates in an evacuated processing chamber.
In semiconductor fabrication, a semiconductor substrate is heated during various temperature activity processes, for example during film deposition, oxide growth and etching. Temperatures associated with processing semiconductor substrates are relatively high, for example typically in a range of about 400.degree. C. to 1150.degree. C.
When heating the substrate, it is preferable to heat the substrate uniformly. Uniform temperature in the substrate provides uniform process variables on the substrate. Uniformity in the process variables is also affected by gas flow uniformity across the substrate. Reduced pressure in the processing chamber also provides enhanced control over the gas flow across the substrate. Therefore, it is highly often desirable to operate these various processes in a reduced pressure environment.
However, when operating in vacuums, heat transfer by convection is effectively zero and heat dissipation is typically limited to heat transfer by conduction and radiation. As a result, in some cases, heaters may not be able to sustain an optimal power output for a given process and, further, may suffer degradation due to the limited heat dissipation. As a result, the performance of heaters is hampered and, further, may have reduced longevity.
Consequently, there is a need for a heater assembly which can operate in vacuum, such as in a processing chamber of a reactor for a processing semiconductor control over the temperature of the substrate and, further, without degrading the heater assembly itself.